CVE-2026-6686
Medium
Description
FatFs R0.16 and earlier contains an uninitialized cluster exposure when f_lseek() extends files beyond EOF without zero-filling newly allocated clusters. This maps to CWE-908 (Use of Uninitialized Resource). Estimated CVSS v3.1 vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N (4.6, Medium). The estimated CISA SSVC vectors are Exploitation: PoC, Technical Impact: Partial.
SeverityMedium
CVSS4.6
Exploit probability—
ProductElm-chan Fatfs
PublishedJul 1, 2026
First seenJul 1, 2026
Weakness typeCWE-908CWE-908
How to fix
Sources list no fixed version or patch link for this vulnerability.
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| elm-chan fatfs | v ≤ r0.16 | — |
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